Phase shifter circuits allow control of insertion phase of a network. They find application in electronic circuitry, such as for example, for shifting the phase of signals propagating on a transmission line. One application in which phase shifters are commonly found is in phased-array and active-array antenna arrangements using transmit-receive (T/R) modules. In general T/R modules include phase shifters for receiving phase shift data and for forming antennae beam patterns and varying the phase of a RF signal.
FIGS. 1 and 2 depict traditional phase shifter equipment. Specifically, FIG. 1 is a block diagram of a conventional phased array radar 100 commonly found in the art. As shown in FIG. 1, phased array radar 100 includes a power source 102 for supplying a predetermined supply voltage 108 to a plurality of T/R modules T/R1, T/R2, . . . T/RN. A supply voltage feed circuit 106 distributes supply voltage 1081, 1082, . . . 108N to the T/R modules T/R1, T/R2, . . . T/RN. Phased array radar 100 additionally includes an exciter 110 for generating RF signals that are fed to a RF signal circulator 114. RF signal circulator 114 is typically configured to provide the RF signals generated by the exciter 110, or RF signals received at a receiver 122, to the T/R modules T/R1, T/R2, . . . T/RN using a signal synthesizing and distribution circuit 116. Particularly, synthesizing and distribution circuit 116 receives the RF signals from circulator 114 and distributes RF signals 1301, 1302, . . . 130i to antennae 132 via T/R modules T/R1, T/R2, . . . T/RN. A control circuit 118 provides control signals 1281, 1282, . . . 128N to the T/R modules T/R1, T/R2, . . . T/RN via a control signal distribution circuit 120. Control signal distribution circuit 120 receives control signal 128 from control circuit 118 and provides control signals 1281, 1282, . . . 128N to T/R modules T/R1, T/R2, . . . T/RN.
FIG. 2 illustrates a conventional T/R module 200 that may be used, for example, as any one of T/R modules T/R1, T/R2, . . . T/RN(FIG. 1). T/R module 200 may include an input/output node 201 for transmitting a RF signal between the RF signal synthesizing and distribution circuit 116 (FIG. 1) and a phase shifter 202 and an input/output node 203 for transmitting a RF signal between an antenna 132 and an amplifier circuit 204. Phase shifter 202 and amplifier circuit 204 may be in communication for transmitting a RF signal therebetween. Moreover, it should be noted that any like numbers shown also in FIG. 1 are discussed above according to this exemplary embodiment of the present invention.
To facilitate understanding of the invention certain naming convention has been adopted. For example, as used herein, a RF signal received from synthesizing and distribution circuit 116 (FIG. 1) is called a “synthesized RF signal 1301-i.” A RF signal received from phase shifter 202 and provided to amplifier circuit 204 is called a “transmission RF signal.” A RF signal received from free space via antenna 132 and provided to amplifier circuit 204 for providing to phase shifter 202, is called a “received RF signal.”
As noted, phase shifter 202 is configured to shift the phase of transmission RF signals according to phase shift data. Amplifier circuit 204 is typically configured to amplify the transmission RF signal up to a predetermined level prior to providing the transmission RF signal to antenna 132, and to amplify received RF signals at a low noise.
A control circuit 206 for receiving a control signal 1281, 1282, . . . 128N from control signal distribution circuit 120 (FIG. 1) outputs a plurality of predetermined phase setting signals (e.g. phase shift data PS1, PS2, . . . PSK) to a level conversion circuit 208. Level conversion circuit 208 typically receives the phase shift data PS1, PS2, . . . PSK from control circuit 206 and converts the phase shift data PS1, PS2, . . . PSK to an output voltage (e.g., converted phase shift data CPS1, CPS2, . . . CPSK) useful for driving the phase shifter 202.
Control circuit 206 is configured to output predetermined phase setting signals PS1, PS2, . . . PSK in accordance with control signals 1281, 1282, . . . 128N. Phase shifter 202 uses the phase setting signals PS1, PS2, . . . PSK in forming antenna beam patterns.
Notably, conventional phase shifters include a number of transistors that receive the phase setting signals PS1, PS2, . . . PSK to enable transistor operation and signal phase shifting. Thus, the phase setting signals PS1, PS2, . . . PSK must be at a voltage level predetermined by the type of transistor used to enable transistor operation. For this purpose, phase shifter 200 may use a level conversion circuit 208 to convert phase setting signals PS1, PS2, . . . PSK to the voltage level required for transistor operation. The converted phase setting signals PS1, PS2, . . . PSK (shown as CPS1, CPS2, . . . CPSK) may then be applied to the phase shifter 202 transistors as described below.
FIG. 3 depicts an exemplary schematic of a conventional phase shifter 202 useful with T/R module 200 (FIG. 2). Phase shifter 202 includes RF input/output terminals 301, 303 that are placed in communication one with the other using a ¼ wavelength transmission line 302. RF input/output terminal 301 may be in communication with an impedance conversion line 306, and RF input/output terminal 303 may be in communication with an impedance conversion line 304, where impedance conversion lines 304, 306 are useful for converting the input impedances of any later connected transistor elements into impedances for obtaining a desired phase shift. The transistors used in the phase shifter 202 are field effect transistors (FET) 308, 310 having their gates in communication with the level conversion circuit 208 (FIG. 2) for receiving converted phase setting signals CPS1, CPS2, . . . CPSK used to turn FETs 308, 310 on and off. FETs 308, 310 have their dc reference terminal 304, 311 placed at ground potential. Converted phase setting signals CPS1, CPS2, . . . CPSK may be biased by bias resistances 312, 314 and applied to the gate of FETs 308, 310 at gate terminals 305, 307 to enable proper FET 308, 310 operation.
One limitation placed on conventional phase shifter design is that gate terminals 305, 307 may only be driven by a voltage polarity consistent with the type of transistor included in the phase shifter 202. For example, for an N-type FET 308, 310 the gate terminal 305, 307 can only be driven with a negative voltage to control FET 308, 310 operation. Thus, converted phase setting signals CPS1, CPS2, . . . CPSK must have a negative polarity when applied to gate terminal 305, 307.
However, with momentary reference to FIG. 2, in some instances, it is desirable to provide the control signals received from control circuit 206 to T/R module circuit elements requiring a positive voltage polarity. For example, where the amplifier circuit 204 is comprised of transistors (not shown) requiring a positive voltage, it is necessary to convert the negative control voltages received from, for example, level conversion circuit 208 (e.g. CPS1, CPS2, . . . CPSK) to voltages having a positive potential. To address this problem, prior art phased-array antenna systems ordinarily used a logic inverter to reverse the polarity of the signal provided by the level conversion circuit. U.S. Pat. No. 6,320,413 discloses exemplary prior art systems and methods for conventional level conversion circuit operable to change the polarity of the control voltages provided by, for example, control circuit 206.
One drawback with the use of logic inverters to change the polarity of the control signals is that the size and power consumption of the T/R module is increased. When overall size and power consumption is a circuit design consideration, such as when the antenna array requires plurality T/R modules operating at high frequencies, it may be desirable to find ways to reduce the number of circuit elements included in the T/R module.